Fuel cell system manifold seal

ABSTRACT

A manifold seal for a fuel cell system includes a sealing area defined by a peripheral portion of a fuel cell stack of the fuel cell system and a portion of an end plate positioned on the fuel cell stack. The manifold seal includes a manifold frame defining a mating surface which sealingly engages the sealing area. The manifold seal also includes a bracket defining a base portion and having a lip projecting from an edge thereof. The base portion is moveably secured to a face of the end plate so that the edge is positioned on the sealing area. The lip is moveably engaged in and cooperates with a slot formed in the mating surface to seal a gap between the mating surface and the sealing area caused by movement of the fuel cell stack.

FIELD OF THE INVENTION

The present invention generally relates to a seal for use in a fuel cellsystem manifold and more specifically relates to sealing a gap betweenthe manifold and an end plate of the fuel cell system.

BACKGROUND OF THE INVENTION

A fuel cell is a device which uses an electrochemical reaction toconvert chemical energy stored in a fuel such as hydrogen or methaneinto electrical energy. In general, fuel cells include an anode tocatalytically react with the fuel and a cathode in fluid communicationwith an oxidant such as air.

Fuel cells are typically arranged in a stacked relationship. A fuel cellstack includes many individual cells positioned between a fixed endplate and a free end plate. One fuel cell stack configuration includesan externally manifolded stack, wherein the fuel cell stack is left openon its sides and a fluid such as a fuel or oxidant is delivered by wayof manifolds sealed to peripheral portions of respective sides of thefuel cell stack. The manifolds thus provide sealed passages fordelivering the fuel and the oxidant gases to the fuel cells anddirecting the flow of such gases in the stack, thereby preventing thosegases from leaking either to the environment or to the other manifolds.

Such manifolds are typically used in Molten Carbonate Fuel Cells (MCFC)which operate at approximately 650° C. During operation of MCFCs, thefuel cells can move relative to the end plates.

SUMMARY OF THE INVENTION

The present invention resides, in one aspect, in a manifold seal for afuel cell system. The manifold seal includes a sealing area defined by aperipheral portion of a fuel cell stack of the fuel cell system and aportion of an end plate positioned on the fuel cell stack. The manifoldseal includes a manifold frame that defines a mating surface whichsealingly engages the sealing area. The manifold seal also includes abracket defining a base portion and having a lip projecting from an edgethereof. The base portion is moveably secured to a face of the end plateso that the edge is positioned on the sealing area. The lip is moveablyengaged in and cooperates with a slot defined by the manifold to seal agap formed between the mating surface and the sealing area caused bymovement of the fuel cell stack during operation.

In one embodiment, the lip of the bracket defines a leg extendinglaterally therefrom. A gasket is positioned in a space between the legand the end plate. The leg slidingly engages the gasket and duringoperation, the leg moves in the slot from a beginning of stack lifesection to an end of stack life section.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a fuel cell system with three manifoldssecured thereto and one manifold disassembled therefrom.

FIG. 2 is a perspective view of a portion of a fuel cell manifold sealwith a portion of a manifold frame and gasket cut away to illustrate abracket.

FIG. 3 is a perspective view of the manifold seal of FIG. 2 having abracket with an elongated leg.

FIG. 4 is a schematic side view of a fixed end portion of the fuel cellsystem of FIG. 1, after operation of the fuel cell system.

FIG. 5 is a schematic side view of a free end portion of the fuel cellsystem of FIG. 1, at the beginning of the fuel cell stack life.

FIG. 6 is a schematic side view of the free end portion of the fuel cellsystem of FIG. 1, at the end of life of the fuel cell stack.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1 a fuel cell system, generally designated by thenumeral 10 includes a Molten Carbonate Fuel Cell (MCFC) stack 12positioned between opposing end plates 14A and 14B. A manifold 16 ispositioned on three of four outwardly facing surfaces 18 of the fuelcell system 10 for directing a fluid such as fuel or an oxidant into orout of the fuel cell stack. A generally rectangular sealing area Sextends around a peripheral portion of each of the outwardly facingsurfaces 18. The sealing area S is defined by a peripheral area P1 ofthe fuel cell stack and portions P2 and P3 of the endplates 14A and 14B,respectively. Each of the manifolds 16 has a portion thereof secured toa portion of the portion P2 of the end plate 14A. During operation ofthe fuel cell system 10, each of the manifolds 16 is moveable relativeto the portions P1 and P3 of the respective sealing area S.

Referring to FIGS. 1 and 2, each of the manifolds 16 includes a manifoldseal, generally designated by the numeral 20. Each manifold seal 20includes a manifold frame 22 defining a mating surface 24. The matingsurface 24 sealingly engages the sealing area S. A portion of the matingsurface 24 of sections 22B and 22C has a slot 26 formed therein andextending longitudinally along a portion of the manifold frames 22B and22C, respectively. Each of the manifold seals 20 has four brackets 28,each defining a base portion 30. The base portions 30 of two of thebrackets 28 are moveably secured to an outwardly facing surface 25 theend plate 14A and the base portions of the other two brackets aremoveably secured to an outwardly facing surface 25 of the end plate 14B.Each of the base portions 30 has a lip 34 positioned at an edge 36thereof and projecting substantially perpendicularly therefrom. The edge36 is positioned on a portion of the sealing area S such that the lip 34moveably engages the slot 26. The lip 34 and the slot 26 are sized tofacilitate movement therebetween and cooperate with one another to seala gap between the mating surface 24 of respective ones of the sections22B and 22C of the manifold frame 22 and corresponding portions of thesealing area S, caused by movement of the fuel cell stack 12, asdescribed below with reference to FIG. 4. The manifold seal 20 can beemployed on new fuel cell systems or retrofit on existing systems.

While the fuel cell system 10 is described as having four outwardlyfacing surfaces 18 each having a generally rectangular sealing area S,the present invention is not limited in this regard, as the manifoldseal 20 can be used on fuel cell systems having any number of facesand/or sealing areas of any shape. Although the manifold seal 20 isshown and described as having four brackets 28, the present invention isnot limited in this regard as more or less than four brackets can beemployed, without departing from the broader aspects disclosed herein.While the fuel cell system 10 is described as including a MCFC stack,the present invention can be employed on fuel cell systems having otherfuel cell stacks, including, but not limited to, solid oxide fuel cellstacks.

As illustrated in FIG. 2, the base portion 30 has a slot 38 extendingtherethrough and through which fastener means 40, for example, ashoulder bolt 42 extends and threads into a threaded bore (not shown)formed in the end plate 14A. In one embodiment, the slot 38 is about 0.5inches in length. The shoulder bolt 42 is secured to the end plate 14Asuch that movement of the bracket 28 is limited, relative to the endplate, to rotation around an axis marked Y and translation along an axismarked X. Thus the bracket 28 is restrained from translation, along anaxis marked Z, relative to the endplate 14A. One or more of the brackets28 can be secured to the other end plate 14B, in a manner similar tothat described above. While the slot is described as being about 0.5inches in length, slots of any length can be employed without departingfrom the broader aspects disclosed herein.

The manifold frame 22 is manufactured from four sections 22A-D of adielectric material to prevent electrical short circuiting betweenindividual cells of the fuel cell stack 12. One section 22A of each ofthe manifold frames 22 is secured to the outwardly facing surface 25 ofthe end plate 14A to restrain movement of the section 22A in a directionalong the Z axis. The end plate 14A is fixed to a support structure (notshown). The manifold seal 20 also includes a gasket 48 formed into ashape complementary to the manifold frame 22 and disposed between themating surface 24 and the sealing area S. A portion of the gasket 48 isremoved to accommodate the base portion 30 and the edge 36 of thebracket 28.

While the manifold frame 22 is described as being manufactured from foursections of a dielectric material, the present invention is not limitedin this regard as other materials can also be employed and the manifoldframe and/or sections 22A-D can be manufactured in any number ofsections without departing from the broader aspects of the presentinvention.

Referring again to FIG. 2, the base portion 30 has a side edge 50positioned adjacent to the fuel cell stack 12 and separated therefrom bya distance D. The distance D is minimized so that the lip 34 can extendsubstantially into the gap thereby improving sealing of the gap. Inaddition, the base portion 30 has a relief 52 tapering inwardly from theside edge 50 to allow the bracket 28 to rotate towards the fuel cellstack 12 without interfering with a ridge portion 54 of the fuel cellstack.

The manifold seal of FIG. 3 is similar to that illustrated in FIG. 2,therefore like elements are assigned like numerals, preceded by thenumber 1. Referring to FIG. 3, each of the manifolds 116 includes amanifold seal, generally designated by the numeral 120. Each of themanifold seals 120 has a manifold frame 122 defining a mating surface124. The mating surface 124 sealingly engages the sealing area S througha gasket 148 positioned therebetween. A portion of the mating surface124 of section 122C has a slot 126 formed therein and extendinglongitudinally along a portion 170 of each of the manifold frames 122C.Section 122B of the manifold frame 122 is configured similar to thatdescribed above for section 122C of the manifold frame 122. The matingsurface 124 of a portion 172 of the section 122D of the manifold frame122 sealingly engages the portion P3 of the sealing area S throughanother portion of the gasket 148.

As illustrated in FIG. 3, the manifold seal 120 includes a bracket 128,defining a base portion 130 moveably secured to an outwardly facingsurface 125 of the end plate 114B. The end plate 114B is free to moverelative to the other end plate 114A and the fuel cell stack 112. Thebase portion 130 has a lip 134 positioned at an edge 136 thereof andprojecting substantially perpendicularly therefrom. The lip 134 has anelongated leg 160 extending laterally from one side 162 thereof and awayfrom the fuel cell stack 112. The edge 136 is positioned on a portion ofthe sealing area S such that the lip 134, including the leg 160,moveably engages the slot 126. A portion of the gasket 148 is removed toaccommodate the base portion 130 and the edge 136 of the bracket 128. Alongitudinal edge 164 of the leg 160 extends over the gasket 148 and isspaced apart therefrom by a distance B to maintain a seal therebetweenwithout damaging the gasket, when the leg moves with the end plate 114B.The lip 134 and the slot 126 are sized to facilitate movementtherebetween and cooperate with one another to seal a gap between themating surface 124 of the frame portion 122 and the sealing area S,caused by movement of the fuel cell stack 112.

As illustrated in FIG. 3, the base portion 130 has a slot 138 extendingtherethrough and through which fastener means 140, for example, ashoulder bolt 142 extends and threads into a threaded bore (not shown)formed in the end plate 114. The shoulder bolt 142 is secured to the endplate 114B such that movement of the bracket 128 is limited, relative tothe end plate, to rotation around an axis marked Y and translation alongan axis marked X. Thus the bracket 128 cannot move, along an axis markedZ, relative to the endplate 114B. In addition, the base portion 130 hasa side edge 150 positioned adjacent to the fuel cell stack 112 andseparated therefrom by a distance D.

Referring to FIG. 4, after many hours of operation of the fuel cellsystem 10, the fuel cell stack 12 expands outwardly in the generaldirection designated by the arrow E. Since the section 22A of themanifold frame 22 is secured to the end plate 14A and the remainder ofthe manifold frame is not fixed to the fuel cell stack 12 or the endplate 14B, the sections 22B, 22C and 22D of the manifold 22 aredisplaced outwardly in the direction of the arrow E by the fuel cellstack. As a result, a gap G is formed between the section 22B of themanifold 22 and the sealing area S, through which fluids in the manifoldcan escape. A similar gap is formed between the section 22C of themanifold 22 and the respective portion of the sealing area S. With thebracket 28 installed on the end plate 14A, the base portion 30 remainsengaged with the end plate. In addition, a portion of the lip 34 slidesout of the slot 26 and the remainder of the lip remains disposed in theslot. As a result, the lip 34 substantially seals the gap G.

Referring to FIG. 5, the fuel cell system 110 is at the beginning oflife (BOL) before consolidation of the fuel cell stack 112 and beforeoperation. In FIG. 5, an outer surface 180 of a distal end 182 of theend plate 114B is shown substantially flush with a distal end 184 of thesection 122C of the manifold frame 122. At BOL, the leg 160 of thebracket 128 is positioned in the slot 126 with a portion of the legdisposed in a beginning of life section 190, adjacent to one end 186 ofthe slot. While the outer surface 180 is shown substantially flush withthe distal end 184, other configurations at BOL are contemplatedincluding but not limited to the outer surface being displaced anydistance away from the distal end.

Referring to FIG. 6, the fuel cell system 110 is at the end of life(EOL) after many hours of operation, during which the fuel cell stack112 consolidates and the end plate 114B moves towards the other endplate 114A in the general direction of the arrow F. The bracket 128moves with the end plate 114B causing the leg 160 to move in the slot126 into an end of life section 192 adjacent to another end 188 of theslot.

In addition, the fuel cell stack 112 can expand outwardly as describedabove with reference to FIG. 4, resulting in the gap G between thesection 122C of the manifold frame 122 and the sealing area S. A similargap can be formed between section 122D of the manifold frame 122 and therespective portion of the sealing area S. However, portions of the leg160 continue to be disposed in the slot 160 after the outward movementof the fuel cell stack 112, such that the gap G is substantially sealed.

Although the present invention has been disclosed and described withreference to certain embodiments thereof, it should be noted that othervariations and modifications may be made, and it is intended that thefollowing claims cover the variations and modifications within the truescope of the invention.

1. A manifold seal for a fuel cell system comprising: a sealing areadefined by a peripheral portion of a fuel cell stack of the fuel cellsystem and a portion of an end plate positioned on the fuel cell stack;a manifold frame defining a mating surface which sealingly engages saidsealing area, said mating surface having a slot formed therein; abracket defining a base portion and having a lip projecting from an edgethereof, said base portion being moveably secured to a face of said endplate so that said edge is positioned on said sealing area; and whereinsaid lip is moveably engaged in and cooperates with said slot to seal agap between said mating surface and said sealing area caused by movementof said fuel cell stack.
 2. The manifold seal of claim 1, wherein saidlip defines a leg extending laterally therefrom.
 3. The manifold seal ofclaim 2, wherein said slot includes a beginning of stack life sectionand an end of stack life section, wherein said leg moves from saidbeginning of life section to said end of life section.
 4. The manifoldseal of claim 2, further comprising a space between said leg and saidend plate through which a gasket is disposed, said leg slidinglyengaging said gasket.
 5. The manifold seal of claim 1, wherein said baseportion is free to move parallel to said face of said end plate.
 6. Themanifold seal of claim 1, wherein said base portion is restrained frommovement perpendicular to said face.
 7. The manifold seal of claim 1,wherein said base portion tapers inwardly from said edge.